Early exposure to cow's milk has benefits: study

NEW YORK (Reuters Health) - A taste of cow's milk during the first two weeks of life may protect a child from later developing an allergy to the milk's protein, a new study suggests.

Cow's milk protein allergy is the most common and most dangerous among the family of dairy allergies and intolerances, with reactions including rash, respiratory and gastrointestinal symptoms, even shock or death.

The finding that giving cow's milk very early in life might boost tolerance came as a surprise to lead researcher Dr. Yitzhak Katz of Tel Aviv University in Israel. He and his colleagues simply set out to improve on current estimates of the number of children with the allergy, and to determine how often it is accompanied by an allergy to soy. "We weren't even looking for a risk factor," he told Reuters Health.

Of 13,000 infants studied, the team found that 66 (0.5 percent) tested positive for the milk allergy -- far fewer than would be expected based on previous population estimates of 1 to 3 percent, they note in the Journal of Allergy and Clinical Immunology.

The researchers also found no link between cow's milk and soy allergies, despite some earlier estimates that up to 1 in 3 children with the first allergy also suffered from the second.

"Soy is a reasonable feeding alternative for children with cow's milk allergy," noted Katz.

But what his team found next most intrigued him. Infants who were first fed cow's milk at the age of 15 days or more had 19 times the risk of developing cow's milk allergy relative to those exposed earlier -- during the first two weeks of life.

Due to common difficulties in digesting the sugar content of cow's milk, some pediatricians have discouraged its introduction until a certain age, Dr. Kari Nadeau of Stanford University in California, who was not involved in the study, told Reuters Health.

Now, it seems there might also be benefits to an earlier start. "It's nice to know that if you do give small amounts of cow's milk to children at an early age," Nadeau said, "it could help prevent their immune system from later viewing this milk protein as a foreign substance and reacting unnaturally to it."

Nadeau noted that further research is needed to pinpoint the most optimal "window of opportunity" and to see how well the exposed babies do as they grow older.

She also cautioned that early feeding of cow's milk is no guarantee that a child won't get the allergy. "At any point in time, if a child starts developing a rash or vomiting to a food," she said, "they should always get checked out by an allergist."

Katz added that the findings should not be interpreted as discouraging breastfeeding. Rather, he recommends simply complementing it with cow's milk early on.

"Let Dad enjoy some midnight infant bonding," he said, "while he delivers a dose or two of cow's milk protein."